In recent years, heating costs have increased rapidly due to the increased costs of fuel oil and natural gas. As a result of rising energy costs, a great number of home owners, especially in the northern states, have begun to utilize various cost efficient means, such as home insulation and wood burning stoves and fireplaces to reduce their winter heating bills.
Another method of reducing energy costs is to make existing furnaces and fireplaces heat more efficiently. During the normal operation of any furnace or fireplace, hot combustion gases are vented into the atmosphere through the furnace flue or chimney. A furnace or fireplace could be made to operate more efficiently if some of the heat from the combustion gases could be recaptured and used to heat the air inside the home.
The present invention is a device for recapturing some of the heat from combustion exhaust gases which may be installed at any convenient location in a chimney or furnace flue.
A number of devices have been patented which, in some way, deal with the recapture of heat from a furnace exhaust flue.
Anable, U.S. Pat. No. 3,930,489 discloses a system for preheating the conditioning air in a forced air furnace. Before entering the furnace heat exchanger, the conditioning air is forced to move in the close proximity of the furnace exhaust stacks. This is accomplished by elongating the exhaust stack between the furnace and the chimney, enclosing the exhaust stock within a hood, adding baffles to promote circulation around the exhaust stacks, and drawing the air through this system by a conventional air forcing means.
Hergenrother, U.S. Pat. No. 2,619,022 discloses a device for preheating air that is to be heated by a furnace located in the basement. The chimney of the device consists of a metallic exhaust stack which is enclosed in a larger pipe. The enclosing pipe has openings for drawing air from the various rooms and from the atmosphere. The lower end of the enclosing pipe is connected by an air duct to the furnace. As air is drawn from the rooms through the enclosing pipe, and into the furnace, it is heated by the exhaust stack.
Smith, U.S. Pat. No. 4,009,705 describes a venting system for a gas fired heater which will eliminate back drafts from the chimney and provides a monitoring device that will shut off the heating system in case of a blocked flue. Increased heating efficiency results from preheating the furnace intake air with heat from the exhaust flue.
Funk, U.S. Pat. No. 3,124,197 discloses a forced air heat exchanging device that is connected to a combustion exhaust flue. The device contains a circular pipe, through which the heated exhaust gases pass, which is surrounded at its exterior surface by a series of air veins. Conditioning air is forced through the air veins, absorbing heat from the walls of the pipe. The air is then directed into a room or other area to be heated.
Konnerth III, U.S. Pat. No. 4,050,628 is another forced air heat exchanger device that is connected at a break in an exhaust stack or flue.
Mayer U.S. Pat. No. 4,050,627 discloses a heat exchanger which extracts heat from an exhaust flue. The heat exchanger is connected at a break in the exhaust stack. A number of small air conduits are located within a heating chamber through which the flue gases are passed. Air which is forced through the air conduit is used for heating the surrounding area. A baffle mechanism within the heating chamber allows the surface area of the air conduit which is exposed to the flue gases to be varied. The amount of heat extracted from the flue gases can thereby be controlled.
Thulman, U.S. Pat. No. 2,634,720 describes means for lowering the surface temperature of a chimney and for producing desirable flue temperature gradients by circulating air in a parallel duct arrangement around the flue. The circulating air is drawn into the duct arrangement through an inlet in the roof or attic and is discharged into the atmosphere near the top of the chimney.
Waterbury, U.S. Pat. No. 1,146,980 describes an apparatus that encloses a section of an exhaust flue and wood or coal burning stove in an exterior housing that is vented to the atmosphere. Air from the room passes into an orifice at the lower end of the housing, absorbs radient heat from the stove and flue, and then passes into the atmosphere creating a circulation and ventilation of air in the room.
Husa, U.S. patent application Ser. No. 146,007 filed May 2, 1980 describes a heat recapture device to be used in connection with a fireplace firebox.
Although the above inventions deal with the extraction of heat from flue gases, none of them disclose a device for installation in a flue which may be produced inexpensively and which can furnish heated forced air and, in addition, induce fresh air circulation into a room.